28.10 : Design Example: Setting a Curve Using Design Data

Designing and plotting a curve using field data requires precise calculations and execution. A horizontal curve with a radius of 200 meters and an intersection angle of 20 degrees is established using the method of perpendicular offsets from the long chord. The long chord, which spans between the curve's endpoints, is calculated to be 69.46 meters in length. To maintain accuracy in plotting, intervals of 3 meters are selected along the chord.

The engineer determines the offset distances for each interval using the offset formula. At the midpoint of the chord, the ordinate value is calculated and validated against the middle ordinate formula of the curve, ensuring the curve's design adheres to precise geometric standards.

The long chord is then marked on the ground, with points identified at 3-meter intervals along its length on either side of the midpoint. For each point, the perpendicular offset distance is measured and marked on the ground at a right angle to the chord. The top ends of these offset points represent the curve’s position at specific intervals.

By connecting the upper ends of the offsets smoothly, the curve is created on the ground, adhering to the design specifications. This method ensures the curve is accurately plotted, providing a reliable framework for the project.